Updated

NASHUA, N.H. -- A 21-year-old man who admitted killing a New Hampshire mother and maiming her daughter in a savage machete and knife attack in their home was convicted of murder Friday, after jurors rejected his claim he was insane at the time.

Christopher Gribble of Brookline will be given an automatic sentence of life in prison without the possibility of parole for his role in the October 2009 attack that killed Kimberly Cates and maimed her 11-year-old daughter Jaimie in their Mont Vernon home.

The jury deliberated approximately two hours over two days before finding him guilty of two counts of first-degree murder, attempted murder, conspiracy to commit murder, conspiracy to commit burglary and witness tampering.

Gribble admitted he took part in the Oct. 4, 2009, home invasion and that he and co-defendant Steven Spader intended to kill anyone they found in the house. Spader was convicted in November and is serving a life sentence.

Gribble took the stand in his own defense during the 11-day trial, claiming he had been abused by his mother and that he had fantasized about torturing and killing her. He asked a jury to find him not guilty by reason of insanity, but prosecution experts who examined him testified Gribble had an anti-social personality but knew the difference between right and wrong.

Juries in New Hampshire have wide latitude to determine what a mental disease or defect is and whether it was the cause of the crimes committed. It has been more than half a century since a New Hampshire jury returned a verdict of not guilty by reason of insanity.